Emulsion polymer and process for preparing the same

ABSTRACT

An emulsion polymer comprising: (a) structural units of a specific polymerizable surfactant, (b) structural units of an ethylenically unsaturated anionic monomer, and (c) structural units of an ethylenically unsaturated nonionic monomer; wherein polymer segments of the emulsion polymer that comprise structural units of the ethylenically unsaturated anionic monomer and structural units of the ethylenically unsaturated nonionic monomer together have specific Hansen solubility parameters. An aqueous coating composition comprising such emulsion polymer provides good early water blister resistance.

FIELD OF THE INVENTION

The present invention relates to an emulsion polymer and a process forpreparing the same.

INTRODUCTION

Aqueous or waterborne coating compositions are widely used in industrialcoating applications, for example, as exterior topcoats in freightcontainer coatings (FCC). Water resistance, especially early waterblister resistance, is typically required for exterior coatings in areasof southern China. After spraying topcoat compositions and drying at 60to 80 degrees Celsius (° C.) for a period of time, some coated freightcontainers are dried at warehouse, while others are moved to outdoor fordrying in the air. For drying the coated containers outdoor, it requiresthe resultant topcoats with sufficient early water blister resistance toavoid blisters caused by the rain, as blisters also have negativeimpacts on appearance and anti-corrosion performance of the coatedfreight containers.

Therefore, it is desirable to provide a polymer, particularly suitablefor coatings, that is capable of providing coatings with early waterblister resistance.

SUMMARY OF THE INVENTION

The present invention provides a novel emulsion polymer particularlysuitable for coating applications without the aforementioned problems.The emulsion polymer prepared in the presence of a specificpolymerizable surfactant comprises polymer segments with specific Hansensolubility parameters. An aqueous coating composition comprising theemulsion polymer of the present invention can provide coatings withexcellent early water blister resistance rated as 10, according to thetest method described in the Examples section below.

In a first aspect, the present invention is an emulsion polymercomprising:

-   -   (a) structural units of a polymerizable surfactant having the        structure of formula (I),

wherein R₁ is a phenyl group or

where R is an alkylene group; m1 is 1, 2, 3 or 4; R₂ is an alkyl or asubstituted alkyl; m2 is 0 or 1; A represents an alkylene group or asubstituted alkylene group, having 2 to 4 carbon atoms; n is an integerin the range of from 1 to 30; and X represents —(CH₂)_(a)—SO₃M or—(CH₂)_(b)—COOM, where a and b are each independently an integer of from0 to 4, and M is an aminium ion having one ethylenically unsaturatedbond;

-   -   (b) structural units of an ethylenically unsaturated anionic        monomer; and    -   (c) structural units of an ethylenically unsaturated nonionic        monomer;    -   wherein polymer segments that comprise structural units of the        ethylenically unsaturated anionic monomer and polymer segments        that comprise structural units of the ethylenically unsaturated        nonionic monomer together have the following Hansen solubility        parameters:

16.42≤δD≤16.64, 2.87≤δP≤3.79, and 3.94≤H≤4.57.

In a second aspect, the present invention is a process of preparing theemulsion polymer of the first aspect. The process comprises: emulsionpolymerization of a monomer mixture comprising an ethylenicallyunsaturated anionic monomer and an ethylenically unsaturated nonionicmonomer in the presence of a polymerizable surfactant, wherein thepolymerizable surfactant has the structure of formula (I),

wherein R₁ is a phenyl group or

where R is an alkylene group; m1 is 1, 2, 3 or 4; R2 is an alkyl or asubstituted alkyl; m2 is 0 or 1; A represents an alkylene group or asubstituted alkylene group, having 2 to 4 carbon atoms; n is an integerin the range of from 1 to 30; and X represents —(CH₂)_(a)—SO₃M or—(CH₂)_(b)—COOM, where a and b are each independently an integer of from0 to 4, and M is an aminium ion having one ethylenically unsaturatedbond;

wherein polymer segments that comprise structural units of theethylenically unsaturated anionic monomer and polymer segments thatcomprise structural units of the ethylenically unsaturated nonionicmonomer together have the following Hansen solubility parameters:

16.42≤δD≤16.64, 2.87≤δP≤3.79, and 3.94≤H≤4.57.

In a third aspect, the present invention is an aqueous coatingcomposition comprising the emulsion polymer of the first aspect.

DETAILED DESCRIPTION OF THE INVENTION

“Aqueous” dispersion or composition herein means that particlesdispersed in an aqueous medium. By “aqueous medium” herein is meantwater and from 0 to 30%, by weight based on the weight of the medium, ofwater-miscible compound(s) such as, for example, alcohols, glycols,glycol ethers, glycol esters, and the like.

“Acrylic” as used herein includes (meth)acrylic acid, alkyl(meth)acrylate, (meth)acrylamide, (meth)acrylonitrile and their modifiedforms such as hydroxyalkyl (meth)acrylate. Throughout this document, theword fragment “(meth)acryl” refers to both “methacryl” and “acryl”. Forexample, (meth)acrylic acid refers to both methacrylic acid and acrylicacid, and methyl (meth)acrylate refers to both methyl methacrylate andmethyl acrylate.

“Structural units”, also known as “polymerized units”, of the namedmonomer, refers to the remnant of the monomer after polymerization, thatis, polymerized monomer or the monomer in polymerized form. For example,a structural unit of methyl methacrylate is as illustrated:

where the dotted lines represent the points of attachment of thestructural unit to the polymer backbone.

“Glass transition temperature” or “T_(g)” reported herein are thosecalculated by using the Fox equation (T.. Fox, Bull. Am. Physics Soc.,Volume 1, Issue No. 3, page 123 (1956)). For example, for calculatingthe T_(g) of a copolymer of monomers M₁ and M₂,

${\frac{1}{T_{g}\left( {{calc}.} \right)} = {\frac{w\left( M_{1} \right)}{T_{g}\left( M_{1} \right)} + \frac{w\left( M_{2} \right)}{T_{g}\left( M_{2} \right)}}},$

wherein T_(g)(calc.) is the glass transition temperature calculated forthe copolymer, w(M₁) is the weight fraction of monomer M₁ in thecopolymer, w(M₂) is the weight fraction of monomer M₂ in the copolymer,T_(g)(M₁) is the glass transition temperature of the homopolymer ofmonomer M₁, and T_(g)(M₂) is the glass transition temperature of thehomopolymer of monomer M₂, all temperatures being in K. The glasstransition temperatures of the homopolymers may be found, for example,in “Polymer Handbook”, edited by J. Brandrup and E. H. Immergut,Interscience Publishers.

“Hansen solubility parameters” as used herein are illustrated by δD, δP,and δH, where δD stands for dispersion (related to van der Waals force),δP stands for polarity (related to dipole moment), and δH stands forhydrogen bonding.

The emulsion polymer of the present invention may be prepared bypolymerization of a monomer mixture in the presence of a polymerizablesurfactant. The emulsion polymer comprises (a) structural units of oneor more polymerizable surfactant. The polymerizable surfactant may havethe structure of formula (I),

wherein R₁ is a phenyl group or

where R is an alkylene group; m1 is 1, 2, 3 or 4; R₂ is an alkyl or asubstituted alkyl; m2 is 0 or 1; A represents an alkylene group or asubstituted alkylene group, having 2 to 4 carbon atoms; n is an integerin the range of from 1 to 30; and X represents —(CH₂)_(a)—SO₃M or—(CH₂)_(b)—COOM, where a and b are each independently an integer of from0 to 4, and M is an aminium ion having one ethylenically unsaturatedbond.

In formula (I), R can be an alkylene group having from 1 to 4 carbonatoms, preferably having from 2 to 3 carbon atoms, such as for example,—CH₂—, —CH(CH₃)—, or —C(CH₃)₂—.

Preferred R₁ is

Preferably, m1 is 2 or 3.

In formula (I), A can be an ethylene group (—CH₂CH₂—). The value of ncan be an integer ranging from 2 to 20 or from 5 to 20.

In formula (I), preferred X is —SO₃M. Preferably, M is

The polymerizable surfactant useful in the present invention istypically an amphoteric surfactant. “Amphoteric surfactant”, also knownas “zwitterionic surfactant”, refers to a surfactant bearing both acidicand basic functionalities and is well known in the art, for example,Amphoteric Surfactants, ed. B. R. Bluestein and C. L. Hilton, SurfactantSeries Vol. 12 Marcel Dekker NY, NY (1982). Amphoteric surfactants mayinclude those having an isoelectric point at pH=3 to pH=8. Theisoelectric point occurs at a characteristic pH for each amphotericsurfactant, and is that pH at which the negative charge on thesurfactant molecule is exactly balanced by the positive charge on thatsame molecule. The amphoteric surfactants may include those havingacidic functionality, especially sulfonated functionality. Sulfonatedmoieties may be present in fully protonated (sulfoacid) form, as saltswith at least one type of cation, or as mixtures of protonated and saltforms. The sulfoacid moieties may also be part of inner salts. As usedherein, inner salt refers to a molecule bearing an anionically chargedmoiety, the counter ion (i.e., cation) for which is also a moietyattached to the that same molecule.

Specific examples of the polymerizable surfactants useful in the presentinvention include the following structure:

where m1 is 2 or 3 and n is as defined above.

The emulsion polymer of the present invention may comprise, by weightbased on the weight of the emulsion polymer, structural units of thepolymerizable surfactant in an amount of 0.5% or more, 0.6% or more,0.7% or more, 0.8% or more, 0.9% or more, or even 1% or more, and at thesame time, 5% or less, 4% or less, 3% or less, 2% or less, or even 1.5%or less. “Weight of the emulsion polymer” in the present inventionrefers to the dry weight of the emulsion polymer.

The emulsion polymer of the present invention may comprise (b)structural units of one or more ethylenically unsaturated anionicmonomer (that is different from the polymerizable surfactant). The term“anionic monomer” herein refers to a monomer that bears an anioniccharge between pH=1-14. The anionically charged moiety of the anionicmonomer typically contains one ethylenically unsaturated bond. Examplesof suitable ethylenically unsaturated anionic monomers include α,β-ethylenically unsaturated carboxylic acids including an acid-bearingmonomer such as methacrylic acid, acrylic acid, itaconic acid, maleicacid, or fumaric acid; or a monomer bearing an acid-forming group whichyields or is subsequently convertible to, such an acid group such asanhydride, (meth)acrylic anhydride, or maleic anhydride; sodium styrenesulfonate (SSS), sodium vinyl sulfonate (SVS),2-acrylamido-2-methylpropanesulfonic acid (AMPS), sodium salt of2-acrylamido-2-methyl-1-propanesulfonic acid, ammonium salt of2-acrylamido-2-methyl-1-propane sulfonic acid; sodium salt of allylether sulfonate; phosphoalkyl (meth)acrylates such as phosphoethyl(meth)acrylate, phosphopropyl (meth)acrylate, phosphobutyl(meth)acrylate, salts thereof, and mixtures thereof;CH_(2═)C(R_(p1))—C(O—O—(R_(p2)O)_(p)—P(O)(OH)₂, wherein R_(p1)═H or CH₃,R_(p2)=alkyl and p=1-10, such as SIPOMER PAM-100, SIPOMER PAM-200, andSIPOMER PAM-300 all available from Solvay; phosphoalkoxy (meth)acrylatessuch as phospho ethylene glycol (meth)acrylate, phospho di-ethyleneglycol (meth)acrylate, phospho tri-ethylene glycol (meth)acrylate,phospho propylene glycol (meth)acrylate, phospho di-propylene glycol(meth)acrylate, phospho tri-propylene glycol (meth)acrylate, allyl etherphosphate, vinyl phosphonic acid, salts thereof, or mixtures thereof.Preferred ethylenically unsaturated anionic monomers are phosphoethylmethacrylate (PEM), acrylic acid (AA), methacrylic acid (MAA), ormixtures thereof. The emulsion polymer of the present invention maycomprise, by weight based on the weight of the emulsion polymer, 0.1% ormore, 0.3% or more, 0.5% or more, 0.75% or more, or even 1% or more, andat the same time, 8% or less, 7% or less, 6% or less, 5% or less, 4.5%or less, 4% or less, 3.8% or less, 3.5% or less, or even 3.3% or less ofstructural units of the ethylenically unsaturated anionic monomer.

The emulsion polymer of the present invention may comprise (c)structural units of one or more ethylenically unsaturated nonionicmonomer (that is different from the polymerizable surfactant), which canbe a monoethylenically or multiethylenically unsaturated monomer. Theterm “nonionic monomer” herein refers to a monomer that does not bear anionic charge between pH=1-14. Suitable monoethylenically unsaturatednonionic monomers may include, for example, vinyl aromatic monomers,C₁-C₂₋-alkyl (meth)acrylates, acrylonitrile (AN), (meth)acrylamide, ormixtures thereof. The C₁-C₂₀-alkyl (meth)acrylates refer to alkyl estersof (meth)acrylic acid containing an alkyl with from 1 to 20 carbonatoms. The C₁-C₂₀-alkyl (meth)acrylates may include C₁-C₃-alkyl(meth)acrylates, cycloalkyl (meth)acrylates, and C₄-C₂₀-alkyl(meth)acrylates that are different from the cycloalkyl (meth)acrylate.Examples of suitable alkyl (meth)acrylates include methyl(meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, iso-butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate,stearyl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl(meth)acrylate, methcyclohexyl (meth)acrylate, dihydrodicyclopentadienyl(meth)acrylate, trimethylcyclohexyl (meth)acrylate, and t-butyl(meth)cyclohexyl acrylate; hydroxy-functional (meth)acrylic acid alkylester such as hydroxyethyl methacrylate and hydroxypropyl methacrylate;glycidyl (meth)acrylate; or mixtures thereof. The vinyl aromatic monomermay include styrene, substituted styrene such as alpha-methylstyrene,trans-beta-methylstyrene, 2,4-dimethylstyrene, ethylstyrene,butylstryene, and p-methoxy styrene; o-, m-, and p-methoxystyrene; andp-trifluoromethylstyrene; or mixtures thereof. Preferredmonoethylenically unsaturated nonionic monomers include methylmethacrylate, styrene, cyclohexyl methacrylate, 2-ethylhexyl acrylate,butyl acrylate, or mixtures thereof. The content of structural units ofthe ethylenically unsaturated nonionic monomer may be adjusted to givethe resultant emulsion polymer with desired Hansen solubilityparameters. For example, the emulsion polymer may comprise, by weightbased on the weight of the emulsion polymer, structural units of butylacrylate preferably in an amount of 35% or more, 36% or more, or even37% or more, and at the same time, 45% or less, 44% or less, or even 43%or less; and structural units of styrene in an amount of 30% or more,31% or more, 32% or more, 33% or more, or even 34% or more, and the sametime, 50% or less, 49% or less, 48% or less, 46% or less, or even 45% orless. Alternatively, the emulsion polymer may comprise, by weight basedon the weight of the emulsion polymer, structural units of 2-ethylhexylacrylate preferably in an amount of 30% or more, 31% or more, or even32% or more, and at the same time, 40% or less, 39% or less, or even 38%or less; and structural units of styrene in an amount of 30% or more,31% or more, 32% or more, 33% or more, or even 34% or more, and at thesame time, 39.5% or less, 39% or less, 38% or less, or even 37% or less.The emulsion polymer may comprise, by weight based on the weight of theemulsion polymer, less than 19% of structural units of acrylonitrile,for example, less than 15%, less than 10%, less than 5%, less than 1%,or even zero of structural units of acrylonitrile. Multiethylenicallyunsaturated nonionic monomers useful in the present invention includedi-, tri-, tetra-, or higher multifunctional ethylenically unsaturatedmonomers. Suitable multiethylenically unsaturated monomers may include,for example, allyl (meth)acrylate, divinyl benzene, ethylene glycoldimethacrylate, butylene glycol dimethacrylate, or mixtures thereof. Theemulsion polymer may comprise, by weight based on the weight of theemulsion polymer, from zero to 3.0%, from 0.05% to 0.8%, or from 0.1% to0.5% of structural units of the multiethylenically unsaturated nonionicmonomer.

The emulsion polymer of the present invention comprises a plurality ofpolymer segments derived from the monomers above by polymerization, forexample, the emulsion polymer comprises segments derived from thepolymerizable surfactant, polymer segments derived from theethylenically unsaturated anionic monomer, and polymer segments derivedfrom the ethylenically unsaturated nonionic monomer. Each polymersegment contains one or more structural units of a monomer. Among these,polymer segments comprising (b) structural units of the ethylenicallyunsaturated anionic monomer and polymer segments comprising (c)structural units of the ethylenically unsaturated nonionic monomer (thatis, all segments that are either derived from the ethylenicallyunsaturated anionic monomer or derived from the ethylenicallyunsaturated nonionic monomer) together demonstrate the following Hansensolubility parameters:

16.42≤δD≤16.64, 2.87≤δP≤3.79, and 3.94≤H≤4.57.

Hansen solubility parameters of polymer segments reported herein arethose calculated using the equations below. For calculating the Hansensolubility parameters of specific polymer segments that comprisestructural units of monomers (i.e., polymer segments derived frommonomers by polymerization), the following equations are used:

δD(calc.)=Σ_(k=1) ^(n)δD(M _(k))*w(M _(k));

δP(calc.)=Σ_(k=1) ^(n)δP(M _(k))*w(M _(k));

δH(calc.)=Σ_(k=1) ^(n)δH(M _(k))*w(M _(k));

wherein δD(calc.), δP(calc.), and δH(calc.) are the calculated Hansensolubility parameters for the polymer segments, w(M_(k)) is the weightfraction of monomer M_(k) in the polymer segments, δD(M_(k)), δP(M_(k)),and δH(M_(k)) are the Hansen solubility parameters for monomer M_(k),and n is the number of monomers in the polymer segments (herein n refersto the number of all anionic and nonionic monomers). Polymer segmentscomprising structural units (b) and structural units (c) herein aretypically those excluding segments comprising structural units of thepolymerizable surfactant in the emulsion polymer. The Hansen solubilityparameters of the monomers can be obtained by using HSPiP software anddatabase (https://www.hansen-solubility.com/HSPiP/) or be referenced to“Hansen Solubility Parameters in Practice—Complete with eBook, softwareand data”, 5^(th) Edition, edited by Steven Abbott, Charles M. Hansenand Hiroshi Yamamoto, published by Hansen-Solubility.com. If the Hansensolubility parameters for a monomer is not available in the HSPiPdatabase, the functional-group-contribution-based ‘Y-MB’ method(https://pirika.com/NewHP/Y-MB/Y-MB.html) in the HSPiP software can beused to calculate the Hansen solubility parameters for such monomer.

The Hansen solubility parameters of some commonly used ethylenicallyunsaturated anionic or nonionic monomers are listed below:

Monomer δD δP δH Butyl acrylate (BA) 15.7 5.5 5.9 Styrene (ST) 17.8 0.61.4 Methyl methacrylate (MMA) 15.55 5.09 6.13 Methacrylic acid (MAA)15.7 5.4 10.5 Acrylonitrile (AN) 15.3 14.3 5.5 2-ethylhexyl acrylate(EHA) 15.8 3 4.1 Hydroxyethyl methacrylate (HEMA) 16.4 7.2 11.3 Allylmethacrylate (ALMA) 15.8 4.1 5 Acrylic acid (AA) 14.7 5.3 12.4 Glycidylmethacrylate (GMA) 16.7 6.6 6.6 Cyclohexyl methacrylate (CHMA) 16.563.12 4.08 Lauryl methacrylate (LMA) 14.4 2.2 5.1

Surprisingly, the emulsion polymer comprising the combination ofstructural units of the polymerizable surfactant with structural unitsof (b) and (c) that afford polymer segments comprising thereof with theHansen solubility parameters above can provide coatings comprising suchemulsion polymer with excellent early water blister resistance rated as10, according to the test method described in the Examples sectionbelow.

The emulsion polymer of the present invention may comprise structuralunits of the polymerizable surfactant, structural units of theethylenically unsaturated anionic monomer, structural units of styrene,and structural units of the alkyl (meth)acrylate. For example, theemulsion polymer comprises, by weight based on the weight of theemulsion polymer, structural units of the polymerizable surfactant,preferably having the structure of

where m1 and n are as defined above,

-   -   structural units of the ethylenically unsaturated anionic        monomer,    -   from 30% to 50% of structural units of styrene,    -   from 35% to 45% of structural units of butyl acrylate, and    -   structural units of cyclohexyl methacrylate, methyl        methacrylate, or mixtures thereof.

Alternatively, the emulsion polymer comprises, by weight based on theweight of the emulsion polymer,

-   -   structural units of the polymerizable surfactant, preferably        having the structure of

where m1 and n are as defined above,

-   -   structural units of the ethylenically unsaturated anionic        monomer,    -   from 30% to 39.5% of structural units of styrene,    -   from 30% to 40% of structural units of 2-ethylhexyl acrylate,        and    -   structural units of cyclohexyl methacrylate, methyl        methacrylate, or mixtures thereof.

Total concentration of structural units in the emulsion polymer is equalto 100%. Types and levels of the monomers described above may be chosento provide the emulsion polymer with a glass transition temperature(T_(g)) suitable for different applications. The emulsion polymer mayhave a T_(g) in the range of from 0 to 60° C., from 10 to 50° C., from15 to 45° C., or from 20 to 40° C. The T_(g) values of the emulsionpolymer can be measured by various techniques including differentialscanning calorimetry (DSC) or calculated by using the Fox equation.

The emulsion polymer of the present invention is typically present in anaqueous dispersion, in which emulsion polymer particles may have anaverage particle size of from 50 nanometers (nm) to 500 nm, from 80 nmto 400 nm, or from 90 nm to 300 nm. The particle size herein refers toZ-average size and may be measured by a Brookhaven BI-90 Plus ParticleSize Analyzer. The aqueous dispersion comprising the emulsion polymermay further comprise water. The concentration of water may be, by weightbased on the total weight of the aqueous dispersion, in the range offrom 30% to 90% or from 40% to 80%.

The emulsion polymer of the present invention may be prepared byemulsion polymerization of a monomer mixture comprising theethylenically unsaturated anionic monomer and the ethylenicallyunsaturated nonionic monomer in the presence of the polymerizablesurfactant. Total concentration of monomers including the polymerizablesurfactant for preparing the emulsion polymer is equal to 100%. Amixture of the monomers for preparing the emulsion polymer may be addedneat or as an emulsion in water; or added in one or more additions orcontinuously, linearly or nonlinearly, over the reaction period ofpreparing the emulsion polymer, or combinations thereof. Temperaturesuitable for emulsion polymerization processes may be lower than 100°C., in the range of from 30 to 95° C., or in the range of from 50 to 90°C.

In the process of preparing the emulsion polymer, free radicalinitiators may be used in each stage. The polymerization process may bethermally initiated or redox initiated emulsion polymerization. Examplesof suitable free radical initiators include hydrogen peroxide, t-butylhydroperoxide, cumene hydroperoxide, ammonium and/or alkali metalpersulfates, sodium perborate, perphosphoric acid, and salts thereof;potassium permanganate, and ammonium or alkali metal salts ofperoxydisulfuric acid. The free radical initiators may be used typicallyat a level of 0.01 to 3.0% by weight, based on the total weight ofmonomers used for preparing the emulsion polymer. Redox systemscomprising the above described initiators coupled with a suitablereductant may be used in the polymerization process. Examples ofsuitable reductants include sodium sulfoxylate formaldehyde, ascorbicacid, isoascorbic acid, alkali metal and ammonium salts ofsulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate,hydrosulfite, sulfide, hydrosulfide or dithionite, formadinesulfinicacid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid,glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaricacid and salts of the preceding acids. Chelating agents for the metalsmay optionally be used.

In the process of preparing the emulsion polymer, the polymerizablesurfactant is used. The polymerizable surfactant may be added prior toor during the polymerization of the monomers, or combinations thereof. Aportion of the polymerizable surfactant can also be added after thepolymerization. The polymerizable surfactants may be used in an amountof from 0.5% to 5%, from 0.6% to 4%, from 0.7% to 3%, from 0.8% to 2%,or from 1% to 1.5%, by weight based on the total weight of monomers usedfor preparing the emulsion polymer. “Monomers used for preparing theemulsion polymer” herein include the polymerizable surfactant.

Preferably, the process of preparing the emulsion polymer is conductedsubstantially free of an additional surfactant that is different fromthe polymerizable surfactant. Additional surfactants may include alkalimetal or ammonium salts of alkyl, aryl, or alkylaryl sulfates,sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts;fatty acids; and ethoxylated alcohols or phenols. “Substantially free”refers to less than 0.8% of the additional surfactant, preferably, lessthan 0.6%, less than 0.5%, less than 0.1%, or even zero, by weight basedon the total weight of monomers used for preparing the emulsion polymer.

In the process of preparing the emulsion polymer, a chain transfer agentmay be used. Examples of suitable chain transfer agents include3-mercaptopropionic acid, methyl mercaptopropionate, butylmercaptopropionate, n-dodecyl mercaptan, benzenethiol, azelaic alkylmercaptan, or mixtures thereof. The chain transfer agent may be used inan effective amount to control the molecular weight of the emulsionpolymer. The chain transfer agent may be present in an amount of fromzero to 3%, from 0.01% to 1%, or from 0.1% to 0.3%, by weight based onthe total weight of monomers used for preparing the emulsion polymer.

The pH value of the obtained aqueous emulsion polymer dispersion may becontrolled to be at least 5, for example, from 6 to 10 or from 6.5 to 9,by neutralization. Neutralization may be conducted by adding one or morebases which may lead to partial or complete neutralization of the ionicor latently ionic groups of the multistage polymeric particles. Examplesof suitable bases include ammonia; alkali metal or alkaline earth metalcompounds such as sodium hydroxide, potassium hydroxide, calciumhydroxide, zinc oxide, magnesium oxide, sodium carbonate; primary,secondary, and tertiary amines, such as triethyl amine, ethylamine,propylamine, monoisopropylamine, monobutylamine, hexylamine,ethanolamine, diethyl amine, dimethyl amine, di-n-propylamine,tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine,3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine,morpholine, ethylenediamine, 2-diethylaminoethylamine,2,3-diaminopropane, 1,2-propylenediamine, neopentanediamine,dimethylaminopropylamine, hexamethylenediamine,4,9-dioxadodecane-1,12-diamine, polyethyleneimine or polyvinylamine;aluminum hydroxide; or mixtures thereof.

The emulsion polymer of the present invention is useful in manyapplications including, for example, wood coatings, metal protectivecoatings, architecture coatings, and traffic paints. The presentinvention also relates to an aqueous coating composition comprising theemulsion polymer. The emulsion polymer may be present, by weight basedon the weight of the aqueous coating composition, in an amount of from10% to 80%, from 20% to 70%, or from 30% to 60%.

The aqueous coating composition of the present invention may compriseone or more pigment. As used herein, the term “pigment” refers to aparticulate inorganic material which is capable of materiallycontributing to the opacity or hiding capability of a coating. Suchmaterials typically have a refractive index greater than 1.8. Examplesof suitable pigments include titanium dioxide (TiO₂), zinc oxide, zincsulfide, iron oxide, barium sulfate, barium carbonate, or mixturesthereof. The aqueous coating composition may comprise one or moreextender. The term “extender” refers to a particulate inorganic materialhaving a refractive index of less than or equal to 1.8 and greater than1.3. Examples of suitable extenders include calcium carbonate, aluminiumoxide (Al₂O₃), clay, calcium sulfate, aluminosilicate, silicate,zeolite, mica, diatomaceous earth, solid or hollow glass, ceramic bead,and opaque polymers such as ROPAQUE™ Ultra E available from The DowChemical Company (ROPAQUE is a trademark of The Dow Chemical Company),or mixtures thereof. The aqueous coating composition may have a pigmentvolume concentration (PVC) of from 5% to 70%, from 10% to 60%, or from15% to 40%. PVC of a coating composition may be determined according tothe equation:

PVC=[Volume_((Pigment+Extender))/Volume_((Pigment+Extender+Emulsion polymer))]×100%.

The aqueous coating composition of the present invention may compriseone or more matting agent. “Matting agent” herein refer to any inorganicor organic particle that provides matt effect. Matting agents usuallyhave an average particle size of 5.5 microns or more according to ASTME2651-10. The matting agents may be selected from silica matting agents,polyurea matting agents, polyacrylate, polyethylene,polytetrafluoroethylene, or mixtures thereof. The matting agent may bepresent, by weight based on the total weight of the aqueous coatingcomposition, in an amount of from zero to 10%, from 0.1% to 7.5%, orfrom 0.5% to 5%.

The aqueous coating composition of the present invention may compriseone or more defoamer. “Defoamer” herein refers to a chemical additivethat reduces and hinders the formation of foam. Defoamers may besilicone-based defoamers, mineral oil-based defoamers, ethyleneoxide/propylene oxide-based defoamers, alkyl polyacrylates, or mixturesthereof. The defoamer may be present, by weight based on the totalweight of the aqueous coating composition, in an amount of from zero to2%, from 0.001% to 1.5%, or from 0.01% to 1%.

The aqueous coating composition of the present invention may compriseone or more thickener (also known as “rheology modifier”). The thickenermay include polyvinyl alcohol (PVA), clay materials, acid derivatives,acid copolymers, urethane associate thickeners (UAT), polyether ureapolyurethanes (PEUPU), polyether polyurethanes (PEPU), or mixturesthereof. Examples of suitable thickeners include alkali swellableemulsions (ASE) such as sodium or ammonium neutralized acrylic acidpolymers; hydrophobically modified alkali swellable emulsions (HASE)such as hydrophobically modified acrylic acid copolymers; associativethickeners such as hydrophobically modified ethoxylated urethanes(HEUR); and cellulosic thickeners such as methyl cellulose ethers,hydroxymethyl cellulose (HMC), hydroxyethyl cellulose (HEC),hydrophobically-modified hydroxy ethyl cellulose (HMHEC), sodiumcarboxymethyl cellulose (SCMC), sodium carboxymethyl 2-hydroxyethylcellulose, 2-hydroxypropyl methyl cellulose, 2-hydroxyethyl methylcellulose, 2-hydroxybutyl methyl cellulose, 2-hydroxyethyl ethylcellulose, and 2-hydoxypropyl cellulose. Preferred thickener is based onHEUR. The thickener may be present, by weight based on the total weightof the aqueous coating composition, in an amount of from zero to 3%,from 0.05% to 2%, or from 0.1% to 1%.

The aqueous coating composition of the present invention may compriseone or more wetting agent. “Wetting agent” herein refer to a chemicaladditive that reduces the surface tension of a coating composition,causing the aqueous coating composition to more easily spread across orpenetrate the surface of a substrate. Wetting agents may bepolycarboxylates, anionic, zwitterionic, or non-ionic. The wetting agentmay be present, by weight based on the total weight of the aqueouscoating composition, in an amount of from zero to 3%, from 0.05% to 2%,or from 0.1% to 1%.

The aqueous coating composition of the present invention may compriseone or more coalescent. “Coalescent” herein refer to a slow-evaporatingsolvent that fuses polymer particles into a continuous film underambient condition. Examples of suitable coalescents include2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycoln-butyl ether, dipropylene glycol methyl ether, propylene glycol methylether, propylene glycol n-propyl ether, diethylene glycol monobutylether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether,triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether,n-butyl ether, Texanol ester alcohol, or mixtures thereof. Preferredcoalescents include Texanol ester alcohol, dipropylene glycol n-butylether, ethylene glycol monobutyl ether, diethylene glycol monobutylether, n-butyl ether, or mixtures thereof. The coalescent may bepresent, by weight based on the total weight of the aqueous coatingcomposition, in an amount of from zero to 8%, from 0.5% to 6%, or from1% to 5%.

The aqueous coating composition of the present invention may furthercomprise water, for example, in an amount of from 30% to 90%, from 40%to 85%, or from 50% to 80%, by weight based on the total weight of theaqueous coating composition.

In addition to the components described above, the aqueous coatingcomposition of the present invention may further comprise any one orcombination of the following additives: buffers, neutralizers,dispersants, humectants, biocides, anti-skinning agents, colorants,flowing agents, anti-oxidants, plasticizers, freeze/thaw additives,leveling agents, thixotropic agents, adhesion promoters, anti-scratchadditives, and grind vehicles. These additives may be present in acombined amount of, from zero to 5%, from 0.001% to 3%, or from 0.01% to2%, by weight based on the total weight of the aqueous coatingcomposition.

The aqueous coating composition of the present invention may be preparedwith techniques known in the coating art, including admixing theemulsion polymer with other optional components as described above.Components in the aqueous coating composition may be mixed in any orderto provide the aqueous coating composition of the present invention. Anyof the above-mentioned optional components may also be added to thecomposition during or prior to the mixing to form the aqueous coatingcomposition.

The aqueous coating composition of the present invention can be appliedto a substrate by incumbent means including brushing, dipping, rollingand spraying. The aqueous coating composition is preferably applied byspraying. The standard spray techniques and equipment for spraying suchas air-atomized spray, air spray, airless spray, high volume lowpressure spray, and electrostatic spray such as electrostatic bellapplication, and either manual or automatic methods can be used. Afterthe aqueous coating composition has been applied to a substrate, theaqueous coating composition may be dried, or be allowed to dry, attemperatures of from 5 to 30° C. for 7 days or more. Alternatively, theaqueous coating composition may be dried at temperatures of from 5 to30° C. for 5 to 30 minutes, and then dried at an elevated temperature,for example, from higher than 40 to 80° C., for 20 to 180 minutes,followed by further drying at temperatures of from 5 to 30° C., thus toform a film (i.e., coating). The aqueous coating composition of thepresent invention can provide coating films obtained therefrom, i.e.,the coatings after drying the aqueous coating composition applied to asubstrate, with excellent early water blister resistance rated as 10according to the test method described in the Examples section.

The aqueous coating composition of the present invention can be appliedto, and adhered to, various substrates. Examples of suitable substratesinclude concrete, cementious substrates, wood, metals, stones,elastomeric substrates, glass or fabrics. The aqueous coatingcomposition is suitable for various coating applications, such asarchitecture coatings, marine and protective coatings, automotivecoatings, wood coatings, coil coatings, and civil engineering coatings.The aqueous coating composition can be used alone, or used as a topcoatin combination with other coatings to form multi-layer coatings. Forexample, the multi-layer coating can be a two-layer coating comprising atwo-component epoxy coating as a base coat and the aqueous coatingcomposition as a topcoat. The multi-layer coating can also be in athree-layer coating comprising a Zinc-containing coating as a primer, atwo-component epoxy coating as a midcoat, and the aqueous coatingcomposition as a topcoat.

EXAMPLES

Some embodiments of the invention will now be described in the followingExamples, wherein all parts and percentages are by weight unlessotherwise specified.

Methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate(EHA), acrylonitrile (AN), and styrene (ST) are available from LangyuanChemical Co., Ltd.

Cyclohexyl methacrylate (CHMA) is available from BASF.

Methacrylic acid (MAA), tert-butyl hydroperoxide (t-BHP), isoascorbicacid (IAA), and ammonium persulfate (APS) are all available fromSinopharm Chemical Reagent Co., Ltd.

AMINOION RE1000 (“RE1000”) surfactant (active content: 30%), availablefrom Nippon Nyukazai Co., Ltd., is a reactive zwitterionic phenolethoxylate surfactant.

HITENOL AR-1025 (“AR-1025”) surfactant (active content: 25%), availablefrom Daiichi Kogyo Seiyaku Co., Ltd., is a polymerizable alkoxylatedtristyrylphenol sulfonate surfactant.

REASOAP SR-1025 (“SR-1025”) surfactant (active content: 25%), availablefrom Adeka Co., Ltd., is a polymerizable alkoxylated sulfonatesurfactant.

SOPROPHOR WA 1802 (“WA 1802”) non-reactive surfactant (active content:31%), available from Solvay, is an ammonia alkoxylated tristyrylphenolsulfonate.

RHODAFAC RS-610 (“RS-610”) non-reactive surfactant (active content:25%), available from Solvay, is a branched alcohol ethoxylate basedphosphate.

DISPONIL FES 32 (“Fes-32”) non-reactive surfactant (active content:30%), available from BASF, is an alkoxylated sulfonate surfactant.

TRITON™0 XN-45S (“XN-45S”) non-reactive surfactant (active content:60%), available from The Dow Chemical Company, is an alkoxylatedsulfonate octylphenol surfactant (TRITON is a trademark of The DowChemical Company).

The following standard analytical equipment and methods are used in theExamples and in determining the properties and characteristics statedherein:

Early Water Blister Resistance Test

The early water blister resistance test was conducted according to ASTMD714-02 method (Standard test method for evaluating degree of blisteringof paints). Coating composition samples were drawn down on Q-Panels(Iron phosphate, R-46) with a wet film thickness of 100 μm. After flashdrying at room temperature for 10 minutes (min), these panels wereplaced into an oven at 75° C. for 30 min, and then dried at roomtemperature for 45 min. The obtained coated panels were immersed intodeionized (DI) water for 7 days, and then observed for surface changesand rated based on the size and area of water blister:

Size-reference standards have been selected for four steps as to size ona numerical scale from 10 to 0, in which No. 10 represents noblistering, No. 8 represents the smallest size blister easily seen bythe unaided eye, and Nos. 6, 4, and 2 represent progressively largersizes.

Frequency-reference standards have been selected for four steps infrequency at each step in size, designated as: Dense (“D”), Medium dense(“MD”), Medium (“M”), and Few (“F”).

Particle Size Measurement

Particle size of emulsion polymer particles in an aqueous polymerdispersion was measured by using a Brookhaven BI-90 or 90Plus ParticleSize Analyzer, which employs the technique of photon correlationspectroscopy (light scatter of sample particles). This method involveddiluting 2 drops of a polymer dispersion to be tested in 20 mL of 0.01 MNaCl solution, and further diluting the resultant mixture in a samplecuvette to achieve a desired count rate (K) (e.g., K ranging from 250 to500 counts/sec for diameter in the range of 10-300 nm, and K rangingfrom 100 to 250 counts/sec for diameter in the range of 300-500 nm).Then the particle size was measured and reported as an average diameterby intensity.

Solid Content of Aqueous Polymer Dispersions

Solids content was measured by weighting 0.7±0.1 g of a sample (wetweight of the sample is denoted as “W1”), putting the sample into analuminum pan (weight of aluminum pan is denoted as “W2”) in an oven at150° C. for 25 min, and then cooling to room temperature and weightingthe aluminum pan with the dried sample with total weight denoted as“W3”. “W3-W2” refers to dry or solids weight of the sample. Solidscontent is calculated as below:

(W3−W2)/W1*100%.

Example (Ex) 1 Aqueous Polymer Dispersion

Preparation of monomer emulsion: A monomer emulsion was prepared bymixing BA (636 grams (g)), MMA (305 g), ST (525 g), MAA (60.3 g), RE1000(30% active, 18 g) and DI water (440 g), and then emulsified withstirring.

Kettle charge: Next, DI water (1,030 g) and RE1000 (30% active, 36.7 g)were charged to a five-liter multi-neck flask fitted with mechanicalstirring.

Monomer feed and polymerization: Contents of the flask were heated to91° C. under a nitrogen atmosphere. To the stirred flask, ammonia (25%active, 2.1 g) in DI water (4 g), the monomer emulsion (95 g) with rinseDI water (43 g), an aqueous solution of APS (2.89 g APS in 17 g DIwater) were added to the reactor. The remaining monomer emulsion,another aqueous solution of APS (1.79 g APS in 55 g water), and asolution of ammonia (25% active, 9 g) in water (45 g) were addedgradually over 120 min. Flask temperature was maintained at 88 ° C.Then, DI water (40 g) was used to rinse the emulsion feed line to theflask. Thereafter, a solution of FeSO_(4.7)7H₂O (0.02 g) andethylenediaminetetraacetic acid (EDTA) (0.07 g) in water (10 g) wasadded to the flask. 1.48 g t-BHP (70% active) in 15 g water, 0.67 g IAAin 15 g water were shot into the flask. Then, aqueous solutions of t-BHP(70% active, 3.36 g) in water (27.2 g) and IAA (1.76 g) in water (30 g)were fed into the flask over 30 min with agitation. The contents of theflask were cooled to room temperature. At last, ammonia (25% active, 10g) in water (20 g) was added as a neutralizer over 10 min to obtain theaqueous polymer dispersion.

Ex 2

Ex 2 was conducted according to the same procedure as Ex 1, except themonomer emulsion was prepared by mixing BA (636 g), MMA (153 g), ST (678g), MAA (60.3 g), RE1000 (18 g, 30% active) and DI water (440 g), andthen emulsified with stirring.

Ex 3

Ex 3 was conducted according to the same procedure as Ex 1, except themonomer emulsion was prepared by mixing EHA (546 g), MMA (395 g), ST(528 g), MAA (60.3 g), RE1000 (18 g, 30% active) and DI water (440 g),and then emulsified with stirring.

Ex 4

Ex 4 was conducted according to the same procedure as Ex 1, except themonomer emulsion was prepared by mixing BA (636 g), CHMA (305 g), ST(525 g), MAA (60.3 g), RE1000 (30% active, 18 g) and DI water (440 g),and then emulsified with stirring.

Comparative (Comp) Ex 1

Comp Ex 1 was conducted according to the same procedure as Ex 1, exceptthe steps of preparation of monomer emulsion and kettle charge were asfollows:

The monomer emulsion was prepared by mixing BA (636 g), MMA (153 g), ST(678 g), MAA (60.3 g), AR-1025 (21 g, 25% active) and DI water (440 g),and then emulsified with stirring. Next, DI water (1,000 g) and AR-1025(60 g, 25% active) were charged to a five-liter multi-neck flask fittedwith mechanical stirring.

Comp Ex 2

Comp Ex 2 was conducted according to the same procedure as Ex 1, exceptthe steps of preparation of monomer emulsion and kettle charge were asfollows:

The monomer emulsion was prepared by mixing BA (636 g), MMA (153 g), ST(678 g), MAA (60.3 g), SR-1025 (25% active, 21 g) and DI water (440 g),and then emulsified with stirring. Next, DI water (1,000 g) and SR-1025(60 g, 25% active) were charged to a five-liter multi-neck flask fittedwith mechanical stirring.

Comp Ex 3

Comp Ex 3 was conducted according to the same procedure as Ex 1, exceptthe steps of preparation of monomer emulsion and kettle charge were asfollows:

The monomer emulsion was prepared by mixing BA (636 g), MMA (305 g), ST(525 g), MAA (60.3 g), WA-1802 (31% active, 17.42 g) and DI water (440g), and then emulsified with 30 stirring. Next, DI water (1030 g) andWA-1802 (31% active, 35.5 g) were charged to a five-liter multi-neckflask fitted with mechanical stirring.

Comp Ex 4

Comp Ex 4 was conducted according to the same procedure as Ex 1, exceptthe steps of preparation of monomer emulsion and kettle charge were asfollows:

The monomer emulsion was prepared by mixing BA (636 g), MMA (305 g), ST(525 g), MAA (60.3 g), RS-610 (25% active, 21 g) and DI water (440 g),and then emulsified with stirring. Next, DI water (1,030 g) and Fes-32(32% active, 34.4 g) were charged to a five-liter multi-neck flaskfitted with mechanical stirring.

Comp Ex 5

Comp Ex 5 was conducted according to the same procedure as Ex 1, exceptthe monomer emulsion was prepared by mixing BA (636 g), ST (830 g), MAA(60.3 g), RE1000 (30% active, 18 g) and DI water (440 g), and thenemulsified with stirring.

Comp Ex 6

Comp Ex 6 was conducted according to the same procedure as Ex 1, exceptthe monomer emulsion was prepared by mixing BA (636 g), MMA (458 g), ST(372 g), MAA (60.3 g), RE1000 (30% active, 18 g) and DI water (440 g),and then emulsified with stirring.

Comp Ex 7

Comp Ex 7 was conducted according to the same procedure as Ex 1, exceptthe monomer emulsion was prepared by mixing BA (636 g), MMA (710 g), ST(220 g), MAA (60.3 g), RE1000 (30% active, 18 g) and DI water (440 g),and then emulsified with stirring.

Comp Ex 8

Comp Ex 8 was conducted according to the same procedure as Ex 1, exceptthe monomer emulsion was prepared by mixing EHA (587 g), ST (653 g), MMA(326 g), MAA (60.3 g), RE1000 (30% active, 18 g) and DI water (440 g),and then emulsified with stirring.

Comp Ex 9

Comp Ex 9 was conducted according to the same procedure as Ex 1, exceptthe steps of preparation of monomer emulsion and kettle charge were asfollows:

The monomer emulsion was prepared by mixing EHA (687 g), AN (299 g), ST(457 g), MAA (60.3 g), XN-45S (60% active, 9 g) and DI water (440 g),and then emulsified with stirring. Next, DI water (1,350 g) and XN-45S(60% active, 18.4 g) were charged to a five-liter multi-neck flaskfitted with mechanical stirring.

Comp Ex 10

Comp Ex 10 was conducted according to the same procedure as Ex 1, exceptthe steps of preparation of monomer emulsion and kettle charge were asfollows:

The monomer emulsion was prepared by mixing EHA (687 g), AN (299 g), ST(457 g), MAA (60.3 g), RE1000 (30% active, 18 g) and DI water (440 g),and then emulsified with stirring. Next, DI water (1,350 g) and RE1000(30% active, 36.7 g) were charged to a five-liter multi-neck flaskfitted with mechanical stirring.

Comp Ex 11

Comp Ex 11 was conducted according to the same procedure as Ex 1, exceptthe monomer emulsion was prepared by mixing BA (731 g), MMA (512 g), ST(219 g), acrylic acid (29.9 g), RE1000 (30% active, 18 g) and DI water(440 g), and then emulsified with stirring.

The monomer composition used in Comp Ex 11 was substantially the same asExample 2 of US2015/0166474A1.

Properties of the obtained aqueous polymer dispersions of Exs 1-4 andComp Exs 1-11 are given in Table 1.

TABLE 1 Properties of Aqueous Polymer Dispersions pH Solids content¹ (%)Particle size² (nm) Viscosity³ (centipoise) Ex 1 8.32 45.95 122 153 Ex 28.28 45.93 124 144 Ex 3 8.13 45.99 120 124 Ex 4 8.1 44.24 111 84 Comp Ex1 8.14 45.62 92 444 Comp Ex 2 8.18 46.03 116 176 Comp Ex 3 8.21 44.23103 86 Comp Ex 4 7.94 43.94 100 100 Comp Ex 5 8.20 45.60 125 125 Comp Ex6 8.24 45.66 118 160 Comp Ex 7 8.14 47.85 113 686 Comp Ex 8 8.04 46.04106 292 Comp Ex 9 7.91 41.50 120 82 Comp Ex 10 7.47 40.40 89 297 Comp Ex11 7.42 44.62 133 44 ¹Solids content and ²Particle size were determinedaccording to the test methods described above. ³Viscosity was determinedby Brookfield viscometer DV-I Primer (60 rpm, spindle #2).

Coating Compositions

The as prepared aqueous polymer dispersions were used as binders forpreparing coating compositions, based on formulations given in Table 2.Ingredients for preparing grinds were mixed using a high speed Cowlesdisperser at 1,200 (rpm) for 30 minutes to form the grinds. Then, theingredients for letdown were added to the grinds using a conventionallab mixer to obtain the coating compositions. For each coatingcomposition, the dosage of the binder and water used in the letdownstage were adjusted to keep solids weight of the binder as 23.14 g andthe total weight of the coating composition as 100 g. The obtainedcoating compositions were evaluated according to the test methodsdescribed above and early water blister resistance properties of theobtained coating films are given in Table 3.

TABLE 2 Coating Compositions Material Name Supplier gram Grind stageWater 6.6 Ammonia neutralizer 0.2 Dispex A40 dispersant BASF 0.3 BYK-181wetting agent BYK Additives & Instruments 0.3 Propylene glycol (PG) asfreeze-thaw agent Sinopharm Chemical Reagent Co., Ltd. 1 TEGO Airex 902Wdefoamer Evonik Industries 0.2 Bentonite-LT extender Guangfu BuildingMaterial Group 0.1 Feldspar extender Guangfu Building Material Group 10Ti-Pure R-902 titanium dioxide The Chemours Company 19 Talc 800 extenderGuangfu Building Material Group 3 Letdown stage Binder Texanolcoalescent Eastman Chemical Company 2.98 Water TEGO Twin 4100 wettingagent Evonik Industries 0.1 Total 100

As shown in Table 3, the binders of Exs 1-4 in which polymer segmentsderived from the anionic and nonionic monomers had the required Hansensolubility parameters (HSP) (δOD 16.42-16.64, δP: 2.87-3.79, and δH:3.94-4.57). The coating compositions comprising these binders (Exs 1-4)all provided coating films with excellent early water blister resistancewith ratings of 10. In contrast, coating compositions comprising bindersprepared in the presence of AR 1025 polymerizable anionictristyrylphenol surfactant (Comp Ex 1), SR 1025 polymerizable anionicallyl surfactant (Comp Ex 2), or non-reactive surfactants (Comp Exs 3, 4and 9) all provided undesirably poor early water blister resistance.Moreover, coating compositions comprising binders in which polymersegments derived from anionic monomers and nonionic monomers had one ormore Hansen solubility parameter falling outside the required ranges(Comp Exs 5-8 and 10-11) all provided coating films with poor earlywater blister resistance.

TABLE 3 Properties of Coating Compositions Binder in coatingcompositions Properties of Binder Calculated HSP values for polymersegments coatings (Aqueous derived from anionic and nonionic monomersused Early water polymer Surfactant used for preparing binders blisterdispersion) for preparing binder δD δP δH resistance Ex 1 RE1000 16.423.79 4.57 10 Ex 2 RE1000 16.64 3.34 4.10 10 Ex 3 RE1000 16.45 2.87 3.9410 Ex 4 RE1000 16.47 3.30 4.10 10 Comp Ex 1 AR-1025 16.42 3.79 4.57 8FComp Ex 2 SR-1025 16.42 3.79 4.57 8M Comp Ex 3 WA-1802 16.42 3.79 4.578M Comp Ex 4 Fes-32 + RS-610 16.42 3.79 4.57 8M Comp Ex 5 RE1000 16.872.89 3.63 6M Comp Ex 6 RE1000 16.19 4.24 5.04 8M Comp Ex 7 RE1000 15.974.69 5.52 8M Comp Ex 8 RE1000 16.58 2.61 3.67 8F Comp Ex 9 XN-45S 16.314.68 3.86 8F Comp Ex 10 RE1000 16.31 4.68 3.86 8F Comp Ex 11 RE100015.94 4.64 5.45 8F

What is claimed is:
 1. An emulsion polymer comprising: (a) structuralunits of a polymerizable surfactant having the structure of formula (I),

wherein R₁ is a phenyl group or

where R₁ is an alkylene group; m1 is 1, 2, 3 or 4; R₂ is an alkyl or asubstituted alkyl; m2 is 0 or 1; A represents an alkylene group or asubstituted alkylene group, having 2 to 4 carbon atoms; n is an integerin the range of from 1 to 30; and X represents —(CH₂)_(a)—SO₃M or—(CH₂)_(b)—COOM, where a and b are each independently an integer of from0 to 4, and M is an aminium ion having one ethylenically unsaturatedbond; (b) structural units of an ethylenically unsaturated anionicmonomer; and (c) structural units of an ethylenically unsaturatednonionic monomer; wherein polymer segments that comprise structuralunits of the ethylenically unsaturated anionic monomer and polymersegments that comprise structural units of the ethylenically unsaturatednonionic monomer together have the following Hansen solubilityparameters:16.42≤δD≤16.64, 2.87≤δP≤3.79, and 3.94≤δH≤4.57.
 2. The emulsion polymerof claim 1, wherein, in formula (I), R₁ is

and m1 is 2 or
 3. 3. The emulsion polymer of claim 1, wherein, informula (I), A represents —CH₂CH₂—, and X represents —SO₃M, where M is


4. The emulsion polymer of claim 1, wherein the ethylenicallyunsaturated nonionic monomer is selected from the group consisting ofstyrene, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate,cyclohexyl methacrylate, or mixtures thereof.
 5. The emulsion polymer ofclaim 1, wherein the emulsion polymer comprises, by weight based on theweight of the emulsion polymer, from 0.5% to 3% of the polymerizablesurfactant.
 6. The emulsion polymer of claim 1 comprising, by weightbased on the weight of the emulsion polymer, structural units of thepolymerizable surfactant having the structure of:

where m1 is 2 or 3, and n is an integer in the range of from 1 to 30;structural units of the ethylenically unsaturated anionic monomer; from30% to 50% of structural units of styrene; from 35% to 45% of structuralunits of butyl acrylate; and structural units of cyclohexylmethacrylate, methyl methacrylate, or mixtures thereof.
 7. The emulsionpolymer of claim 1 comprising, by weight based on the weight of theemulsion polymer, structural units of the polymerizable surfactanthaving the structure of

where m1 is 2 or 3, and n is an integer in the range of from 1 to 30;structural units of the ethylenically unsaturated anionic monomer; from30% to 40% of structural units of styrene; from 30% to 39.5% ofstructural units of 2-ethyl hexyl acrylate; and structural units ofcyclohexyl methacrylate, methyl methacrylate, or mixtures thereof.
 8. Aprocess for preparing the emulsion polymer of claim 1 comprising:emulsion polymerization of a monomer mixture comprising an ethylenicallyunsaturated anionic monomer and an ethylenically unsaturated nonionicmonomer in the presence of a polymerizable surfactant, wherein thepolymerizable surfactant has the structure of formula (I),

wherein R₁ is a phenyl group or

where R₁ is an alkylene group; m1 is 1, 2, 3 or 4; R₂ is an alkyl or asubstituted alkyl; m2 is 0 or 1; A represents an alkylene group or asubstituted alkylene group, having 2 to 4 carbon atoms; n is an integerin the range of from 1 to 30; and X represents —(CH₂)_(a)—SO₃M or—(CH₂)_(b)—COOM, where a and b are each independently an integer of from0 to 4, and M is an aminium ion having one ethylenically unsaturatedbond; wherein polymer segments that comprise structural units of theethylenically unsaturated anionic monomer and polymer segments thatcomprise structural units of the ethylenically unsaturated nonionicmonomer together have the following Hansen solubility parameters:16.42≤δD≤16.64, 2.87≤δP≤3.79, and 3.94≤δH≤4.57.
 9. An aqueous coatingcomposition comprising the emulsion polymer of claim 1.